Random Drops In Rpms?

[jro909]

recently i have been having the issue of the truck dropping below idle speed and sputtering before going back up to idle speed...first it started when applying the brakes firmly and at low rpms then now it does it if i hit the gas enough to coast to a stop sign, once let off the rpms drop below 500 the engine hesitates then goes back up to 500 rpms....this problem does not occur everytime i've driven it, its quite random...any ideas? it also seems to do it if i put the truck in park, once put in park the truck hesitates down to below 500 rpms then back up and its fine, the truck itself idles fine

[XYZ]

Sounds like another possible "cleaning the throttle body" deal. A couple of years ago, mine would drop idle, especially if I was turning around in a driveway to head back in the other direction, with the wheels cut all the way over left or right, adding a little strain to the idle.

[jro909]

i think i discovered what it is, the air intake is rather loose when it meets the throttle body....anybody know if this would do it? and how tight is that clamp suppose to be?

[XYZ]

If you suspect air is getting in at that point, then yes, because the air is getting in after the MAF sensor (unmetered), thus too much air for the amount of fuel the computer is trying to provide. Just snug the clamp up & see what happens.

[DSN46]

Wow! I have been chasing this problem for some time now. I have, removed and cleaned throttle body thoroughly.... replaced MAP Sensor.... cleaned the MAF sensor.... replaced original plugs and wires with AC/Delco plugs and Taylor wires.... replaced fuel filter..... replaced Fuel Pressure Regulator.... wiggled wires and removed and cleaned ALL of the grounds on the engine and chassis. NONE of it has worked yet.

 

I will keep trying and let you know if I come find the culprit. Please let us know if YOU find it... it is getting on my nerves now. :-)

 

James

[98trck]

my Wife's'04 trailblazer was doing same thing and some times we would smell raw gas

took it too the dealer it was fuel pressure regulator going bad, and leaking

appearatly it happens often the service rep knew what it was when we told him the symptoms

PETE

[DSN46]

Unfortunately, I have already replaced the Fuel Pressure Regulator. I used an aftermarket from BWD (Advance Auto Parts), but I dont think that would make much difference.

 

jro909 did you ever find out your problem?

 

Thanks

[jro909]

my air intake was a little loose that the throttle body so i tightened it down and it seemed to work, a guy i work with found it...the tube so loose enough to be pulled off by hand, so my theory was that when the area was cold the tube was quite loose and once it heated up it would clamp on the throttle body lip more...so far so good, check it out and lmk if it works

[DSN46]

my air intake was a little loose that the throttle body so i tightened it down and it seemed to work, a guy i work with found it...the tube so loose enough to be pulled off by hand, so my theory was that when the area was cold the tube was quite loose and once it heated up it would clamp on the throttle body lip more...so far so good, check it out and lmk if it works

 

 

Thanks for the reply! Unfortunately, a loose intake tube isn't my problem... man I wished! I guess I'll just have to keep testing and searching until I find the problem.

 

Take care,

 

James

[jro909]

my air intake was a little loose that the throttle body so i tightened it down and it seemed to work, a guy i work with found it...the tube so loose enough to be pulled off by hand, so my theory was that when the area was cold the tube was quite loose and once it heated up it would clamp on the throttle body lip more...so far so good, check it out and lmk if it works

 

 

Thanks for the reply! Unfortunately, a loose intake tube isn't my problem... man I wished! I guess I'll just have to keep testing and searching until I find the problem.

 

Take care,

 

James

 

 

the only constant event i can link to the random drop in rpms is, the truck being semi cold(below the first mark on temp guage) and stopping quick...i thought maybe the fuel was getting pushed away from the pump or somethen because i have a 36 gallon tank that i keep half filled but that seems unlikely...i also thought my exhaust leak could be causing it but that also seems unlikely...idk where the hell is bob the tech when ya need him